Planes rendered into two triangles of different colors?
For future readers: (TL;DR) This triangle effects can be removed by enabling Auto Smooth under mesh settings.

Credits to @DuarteFarrajotaRamos:


  Is your mesh smooth shaded? It looks like it is flat shaded ,so non
  planar quads will inevitably show visible sharp edge. Make your mesh
  smooth shaded, check Auto Smooth under Mesh Data in the Properties
  Window or add an Edge Split modifier. You may need to manually mark
  some edges as Sharp in Edit Mode if you have a mix of Smooth and Flat
  shaded areas in the same object